Key Points
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Degenerative joint disease is the foremost medical condition leading to operations in the United States. With continued population growth and an increasing percentage of older people, a fivefold increase in the demand for hip and knee arthroplasty and spine procedures is projected by 2030.
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Many orthopedic operations including total joint arthroplasties and spine surgeries are classified as intermediate surgical risk, with 30-day cardiac death or myocardial infarction occurring with an incidence of 1% to 5%. Since preoperative cardiac risk evaluation is often inconclusive in high-risk patients with limited mobility, a higher level of monitoring and perioperative troponin measurements should be considered to assess for perioperative cardiac events.
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Comprehensive preoperative geriatric assessment is increasingly used in the perioperative care of older patients who may have multiple comorbid conditions and who have suffered fragility fractures. Prehabilitation programs can be useful in these patients to reduce frailty and improve surgical outcome.
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Fractures of the proximal femur following falls are common in older patients and are associated with high morbidity and mortality. Early surgery (<24 hours) has been associated with reduced pain and length of hospital stay. Patients with significant medical comorbidities that delay surgery for more than 4 days have a higher mortality.
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As compared to the lateral position, beach chair position offers superior surgical exposure and access for most shoulder surgeries, less distortion of muscle anatomy, and less tension on the brachial plexus. Cerebral perfusion pressure can decrease by 15% in sitting patients under general anesthesia, and in patients with cerebrovascular disease detrimental decrease in cerebral blood flow can occur if the systemic pressure is not carefully monitored and maintained. The role of the sitting position on postoperative neurologic outcome remains, however, controversial.
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The most common complications after total hip arthroplasty and total knee arthroplasty are cardiac events, pulmonary embolism, pneumonia and respiratory failure, and infections. Older patients with major comorbidities including cardiac disease, pulmonary disease, and diabetes should have a complete preoperative medical evaluation.
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Cemented fixation of the femoral prosthesis can be complicated by the bone-cement implantation syndrome, resulting in intraoperative hypotension, hypoxia, or even cardiac arrest. Invasive hemodynamic monitoring with an arterial catheter and possibly also a central venous catheter should be considered. Treatment with a potent inotropic agent such as epinephrine may be required. Pulsatile lavage of the femoral canal and drilling a vent hole in the femur before prosthesis insertion can also ameliorate the hemodynamic consequences of this devastating complication.
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Correction of spinal deformities can be associated with large intraoperative blood loss, and measures to minimize blood transfusion should be considered. Deliberate controlled hypotension has been employed but must be used with caution in older adults, those with cardiovascular disease, or those at risk for ischemic complications and postoperative vision loss. Antifibrinolytic agents may be considered to limit blood loss but should be avoided in patients with a history of thromboembolic events, coronary stents, or renal impairment.
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Intraoperative neurophysiologic monitoring is increasingly employed for spine surgeries and is currently recommended for procedures with increased risk for spinal cord injury including correction of spine deformities, resection of intramural tumors, unstable spine trauma, Chiari malformation, spinal cord vascular malformations, as well as those with risk for root damage and in patients with significant risk for compression neuropathies.
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Perioperative visual loss after spine surgery can be caused by anterior or posterior ischemic optic neuropathy, retinal ischemia, cortical blindness, or posterior reversible encephalopathy. Direct pressure on the eye should be avoided and patients should be positioned so that the head is level with or higher than the heart. The patient’s head should be maintained in a neutral forward position without significant neck flexion, extension, lateral flexion, or rotation. Staged spine surgery procedures can reduce the risk of perioperative visual loss and should be considered in high-risk patients.
Acknowledgment
The editors and publisher would like to thank Dr. Michael K. Urban for contributing a chapter on this topic in the prior edition of this work. It has served as the foundation for the current chapter.
Preoperative Evaluation
Epidemiology and Demographics of Orthopedic Surgery
Orthopedic operations represent the most frequently performed procedures in U.S. hospitals. Arthroplasty of the knee was the single operation performed most often during U.S. hospital stays in the year 2012, amounting to 700,100 operating room procedures (223 per 100,000 population). Hip replacement surgery with 468,000 operations (149 per 100,000 population) was the fourth most frequent operation and spinal fusion, with 450,900 operations (144 per 100,000 population), the fifth.
These statistics highlight the magnitude of degenerative joint disease, or osteoarthritis (OA), as the foremost medical condition leading to operations in U.S. hospitals. OA is the most common form of arthritis, affecting over 54 million U.S. adults according to 2018 data (78 million U.S. adults are expected to be affected in the year 2045). The lifetime risk of developing OA of the knee is about 46%, and that of the hip is 25% according to the Johnston County Osteoarthritis Project.
With age as a prominent risk factor for developing osteoarthritis and with an increasing percentage of elderly people in general, termed population aging (we are expecting 83.7 million US citizens older than 65 years in 2050, almost double the 2012 estimate of 43.1 million for that age group) ( Fig. 64.1A and B ), the demand for primary total knee arthroplasty is projected to increase by the year 2030 by approximately 5-fold, amounting to 3.4 million surgeries expected to be performed annually in the US ( Fig. 64.2A and B ).
Given the increasing number of patients and volume-based need for orthopedic surgery, every anesthesiologist will sooner or later become an orthopedic anesthesiologist. Population aging with the corresponding low support ratio (defined by the number of workers divided by retirees) will also inevitably cause political and financial pressures on public healthcare systems. In particular, financial pressures will certainly intensify and be passed on to orthopedic surgery and anesthesia with its age-related increase in frequency and volume.
It is not surprising that in 2013 the OA-attributable medical costs in the United States were estimated to be $140 billion, with the total medical expenditures and earning losses as high as $304 billion. When conservative therapy including physical activity with muscle strengthening, flexibility and balance exercises, weight control, pain medications, and other personal coping strategies fail to control the symptoms of OA, joint replacement surgery is often the last option for patients suffering from OA to relieve pain and regain mobility.
Using the traditional accounting method, the total cost per hip replacement was recently estimated to be 22,000 to 27,000 USD, and for the total cost per knee replacement, 29,500 USD. It is, therefore, not surprising that OA is among the most expensive medical conditions to treat when joint replacement surgery is required. In fact, OA was, following septicemia, the second most expensive health condition treated at U.S. hospitals in 2013. In that year, OA accounted for $16.5 billion, or 4.3% of the combined costs of all U.S. hospitalizations. OA was also the most expensive condition for which privately insured patients were hospitalized, accounting for over $6.2 billion in hospital costs and amounting to 3.6% of the combined costs for all private hospitalizations.
In the past, there was a natural reluctance to perform total joint arthroplasties on very old patients. Older studies reported not only limited evidence of favorable pain and functional outcome of these procedures in patients aged 80 years or older, but also higher rates of complications and mortality. Some of these studies were undersized, only used a descriptive or retrospective design, and were also challenged by case-control or prospective community-based studies that failed to report higher complication rates in older age groups. The main conclusion of these authors was that with increased life expectancy and elective surgery improving the quality of life, age alone is no longer a factor that affects the outcome of total joint arthroplasty and should, therefore, not be a limitation when deciding who should receive this surgery. Over the past 20 years, arthroplasties in octogenarians and even nonagenarians have become routine procedures in many orthopedic institutions. Nevertheless, a recent study including 7569 patients reported a greater risk of perioperative mortality (relative risk [RR] 3.69; confidence interval [CI], 1.37-9.93), pneumonia, and urinary tract infection in patients 80 years of age or older undergoing aseptic revision total hip arthroplasty (THA). This same study also found general anesthesia compared with epidural, spinal, regional, or monitored anesthesia care to be an independent risk factor for serious adverse events in these patients (RR 1.90; 95% CI, 1.29-2.79).
Considering this enormous financial expenditure combined with the increased age and accompanying comorbidities of the orthopedic patients, anesthesiologists must be highly skilled and apply their utmost vigilance when planning the anesthetic course, including counseling the patient, identifying at-risk patients, and selecting appropriate perioperative anesthetic management and postoperative care.
Cardiovascular Comorbidities
Coronary Artery Disease
With regard to cardiac risk, surgical interventions can be broadly divided into low-risk, intermediate-risk, and high-risk groups with estimated 30-day cardiac events (cardiac death and myocardial infarction) of less than 1%, 1% to 5%, and more than 5%, respectively. The vast majority of orthopedic operations, such as total joint arthroplasties and spine surgery, are considered and classified as an intermediate surgical risk with 30-day cardiac death or myocardial infarction occurring in 1% to 5% of patients. In fact, most studies have reported a primarily perioperative, acute myocardial infarction rate after hip or knee arthroplasty of 0.3% to 1.8%. A recent study defining the intrinsic cardiac risk of a single specified operation rather than groups of operations to improve upon current preoperative cardiac-risk assessment strategies also considered THA as an intermediate intrinsic cardiac risk with an odds ratio (OR) of 0.95 (95% CI, 0.83-1.08) relative to the statistically estimated average procedure. Another interesting study, using matched controls not undergoing surgery, demonstrated an increased risk of acute myocardial infarction during the first 2 weeks after total hip replacement (25-fold) and after total knee replacement (31-fold). The association of an increased cardiac risk and surgery was strongest in patients 80 years of age or older. Interestingly, the risk of acute myocardial infarction decreases significantly after 2 weeks, although it remains elevated during the first 6 weeks for total hip replacement patients ( Fig. 64.3 ).
Over the last 40 years, several indices and scores were developed to better determine perioperative cardiac risk. The first was introduced in 1977 by Lee Goldman. The most widely used of these risk indices today remains the Revised Cardiac Risk Index (RCRI). More recently, a new perioperative risk index known as the Gupta score was proposed using a new model and an up-to-date and simplified approach, which is also available as a risk calculator on the Internet. It was validated on a cohort of more than 400,000 patients of the National Surgical Quality Improvement Program database and uses the American Society of Anesthesiologists (ASA) classification system, dependent functional status, age, abnormal creatinine, and type of surgery as main factors associated with cardiac risk after surgery. In this study, the adjusted OR for myocardial infarction or cardiac arrest was estimated to be 2.22 (95% CI, 1.55-3.17) for orthopedic surgery and 1.24 (95% CI, 0.38-4.00) for spine surgery, compared with an OR of 4.96 for aortic surgery. With a growing geriatric population and an increase in elective noncardiac surgeries in these patients, the necessity of having accurate estimations of the cardiac risk for geriatric patients becomes obvious. For this reason, the new geriatric-sensitive perioperative cardiac risk index (GSCRI), derived solely from geriatric data, was developed in 2017. The GSCRI model contains a total of seven variables, where the main three statistically important variables associated with cardiac risk in the older adult were stroke history, ASA class, and surgical category. Compared to the Gupta score, the GSCRI model considers heart failure, stroke history, and diabetes mellitus status as additional variables. The GSCRI has been shown to be a significantly better predictor of cardiac risk in geriatric patients undergoing noncardiac surgery compared to the Gupta score and RCRI. In the GSCRI, the OR for myocardial infarction or cardiac arrest in orthopedic patients (OR, 2.99; 95% CI, 2.22-4.02) was higher than in the other two indices. The underestimated cardiac risk in geriatric patients resulting from these scores is likely due to estimates that were derived from a younger population.
During the last few years, the focus of cardiac risk has somewhat changed, and perioperative myocardial injury (PMI) has gained increased importance as an additional risk factor for postoperative cardiac events. High-sensitivity cardiac troponin assays have been introduced as an important biomarker in routine clinical care. Such novel biomarkers can detect patients at risk beyond established risk scores, and the measurement of these troponins allows for detection of acute cardiomyocyte injury during the perioperative period. PMI is mainly defined by a perioperative increase of absolute or relative troponin values using delta or maximum postoperative values. Despite the current lack of a clear and uniform international definition for PMI, this entity has recently been identified as an important, yet often undetected, complication of noncardiac surgery that is strongly associated with 30-day mortality. In the most recent study on PMI, Puelacher and coauthors defined PMI as an absolute increase in high-sensitivity cardiac troponin of 14 ng/L or greater from preoperative to postoperative measurements in high-risk patients 65 years or older or in patients 45 years or older with a history of preexisting coronary artery disease, peripheral artery disease, or stroke. In their study population of over 2000 patients, they found an incidence of PMI in orthopedic patients undergoing an intermediate-risk surgical procedure (e.g., total hip or knee replacement) of 20% and for spinal surgery an incidence of PMI of 15% ( Table 64.1 ). With PMI being associated with an overall substantial 30-day mortality as high as 9% and 1-year mortality as high as 22%, recommendations have already been published for screening high-risk patients for PMI. The Canadian Cardiovascular Society Guidelines on perioperative cardiac risk assessment and management of patients undergoing noncardiac surgery already explicitly recommend obtaining daily troponin measurements for 48 to 72 hours after noncardiac surgery in high-risk patients. These perioperative troponin measurements may be particularly useful in high-risk orthopedic patients, since the preoperative cardiac risk evaluation is often inconclusive due to the limited mobility in these patients.
| Incidence of PMI [95% CI] | ESC/ESA Surgical Risk | |||
|---|---|---|---|---|
| <1% | 1-5% | >5% | ||
| All surgical specialties | 16% [14-17] (397/2546) | 9% [9-13] (79/833) | 17% [19-23] (248/1432) | 25% [28-39] (70/281) |
| Orthopedic | 16% [12-20] (50/315) | 10% [6-18] (12/115) | 20% [15-26] (36/183) | 12% [2-36] (2/17) |
| Trauma | 18% [15-22] (83/455) | 12% [8-17] (22/188) | 23% [19-29] (61/260) | 0% [0-41] (0/7) |
| Spinal | 15% [11-19] (55/372) | 19% [6-44] (3/16) | 15% [11-19] (52/356) | 0% [0] (0/0) |
Other Cardiac Comorbidities
Coronary artery disease is probably the single most important cardiac risk factor in orthopedic patients. However, other cardiac diseases such as valvular heart disease or pulmonary hypertension are also important to detect and assess during the preoperative evaluation. Pulmonary hypertension is particularly important in orthopedic patients. In light of the effect of a potentially increased intrathoracic pressure on right heart diastolic function during certain procedures and positioning, the increased risk of venous thromboembolism and the risk of pulmonary embolism of intramedullary contents including fat, bone debris, and cement possibly exacerbating and worsening preexisting right heart strain need to be considered.
Pulmonary hypertension is hemodynamically defined as a resting mean pulmonary arterial pressure of 25 mm Hg or greater and is classified into five groups: (1) patients with primary pulmonary arterial hypertension, (2) patients with pulmonary hypertension due to left heart disease, (3) patients with pulmonary hypertension due to chronic lung disease and/or hypoxia, (4) patients with chronic thromboembolic pulmonary hypertension, and (5) patients with unclear, mixed, or multifactorial reasons for pulmonary hypertension. A number of retrospective studies reported the considerable risk of morbidity and mortality in patients with pulmonary hypertension undergoing noncardiac surgery with mortality ranging from 3.5% to 18%. Major or emergency surgery, long procedure (more than 3 hours), high ASA class score, concomitant cardiovascular disease, poor exercise tolerance, higher preoperative pulmonary artery pressure, and the diagnosis of primary arterial hypertension have all been associated with adverse outcomes in these patients. Ramakrishna and associates retrospectively identified 146 patients with pulmonary hypertension undergoing various noncardiac surgical interventions and reported a mortality rate of 7%. When the authors stratified risk by type of surgery, they found that 17% of patients undergoing low-risk surgical procedures experienced morbidity compared with 48% of those undergoing orthopedic surgery. This suggests that patients with pulmonary hypertension undergoing orthopedic surgery represent an especially vulnerable group. Other authors examined 1359 patients with pulmonary hypertension undergoing THA and 2184 patients with pulmonary hypertension undergoing TKA. In-hospital mortality rates among patients with pulmonary hypertension increased by a factor of 3.72 (95% CI, 2.13-6.39) for the cohort undergoing hip arthroplasty compared with controls and by a factor of 4.55 (95% CI, 2.16-9.39) in patients undergoing TKA. The highest rate of in-hospital mortality with 5% was reported in patients with primary pulmonary hypertension undergoing hip arthroplasty.
A thorough clinical examination of a patient with pulmonary hypertension should focus on the nature of symptom progression, exercise tolerance, signs of right ventricle failure, heart rate, blood pressure, electrocardiogram (ECG), chest radiography and biomarkers (B-type natriuretic peptide and high-sensitivity cardiac troponins). Further investigations may include arterial blood gases, echocardiography with estimation of pulmonary artery pressure, computed tomography (CT), coronary angiography, or even advanced and invasive hemodynamic measurements of pulmonary artery pressures and cardiac output depending on the severity of the disease. Mortality of these surgical procedures can be reduced with careful planning, ideally in tertiary nationally designated pulmonary hypertension centers with close preoperative, intraoperative, and postoperative hemodynamic monitoring to prevent a pulmonary hypertension crisis.
Finally, it is important to also consider the noncardiac risks in the orthopedic population. At the moment, there is a lack of data on how noncardiac risk factors such as preoperative mental status, level of dependency, anemia, extreme low or high body weight, pulmonary risk factors, and immune status interact with the cardiovascular risk factors described earlier and how they impact the outcome of orthopedic surgery. There is a need for more general risk scores that can predict the outcome and mortality from noncardiac causes. Therefore, in geriatric orthopedic patients it might be beneficial to obtain a more comprehensive estimation of a patient’s functional reserves during the preoperative evaluation. This would also include noncardiac risk factors, rather than focusing on single-organ function and biomarkers alone. Too many healthcare systems are still organized around single-system illnesses. Today, frailty is increasingly recognized as an age-associated, multidimensional syndrome and a unique domain of health status that can be a valid marker of decreased reserves and of resulting perioperative vulnerability and unfavorable postoperative outcome in older patients.
Frailty
It has long been known that older patients are at increased risk for postoperative complications, possibly due to reduced physiologic reserves to withstand an operation. Linda Fried was the first to use a validated scoring system to define this vulnerability (or frailty) in a more standardized manner and found that such preoperative characterization of frailty using five domains (weight loss, decreased grip strength, exhaustion, low physical activity, and slowed walking speed) could predict surgical outcomes such as postoperative complications, length of hospital stay, and discharge to a skilled- or assisted-living facility. Her frailty score also augmented other risk-assessment models such as the ASA score, the RCRI, or the Eagle’s cardiac risk index. Since the first description of this frailty concept in surgical patients, many additional frailty scores and scales including a vast diversity of variables have been proposed in the literature.
In orthopedic surgery, the Clinical Frailty Scale, the FRAIL scale, the modified Frailty Index (mFI), the Groningen Frailty Indicator (GFI) questionnaire, and the Frailty Phenotype and Frailty Index have all been used. Flexman and associates showed in 52,671 patients that approximately 4% of the spine surgery population is frail and that the mFI independently predicted major postoperative complications (unadjusted odds ratio 1.58), prolonged length of stay (unadjusted odds ratio 1.89), discharge to a higher level of care (unadjusted odds ratio 2.29), and 30-day mortality (unadjusted odds ratio 2.05 for every 0.1 increase in frailty score) in patients undergoing surgery for degenerative spine disease. In another study to assess feasibility and validity of the GFI questionnaire in patients undergoing total hip or knee arthroplasties, the authors reported that 33% of patients with hip OA and 24% of patients with knee OA were frail. All studies examining frailty in elderly orthopedic patients reported a significant association with adverse postoperative outcomes such as surgical complications, hospital length of stay, discharge to post-acute institutional care, and readmission rate within 30 days.
It has to be pointed out that frailty scales should be accompanied by a thorough clinical examination and comprehensive geriatric assessment including examining the burden of comorbidity, polypharmacy, physical function, psychological status, nutrition, risk of postoperative delirium, and social support to add further insights into the actual risk and the patient’s real expectations. Well-crafted comprehensive geriatric assessments can be a more powerful predictor of perioperative risk than the ASA score. A study in older patients with a mean age of 78 years examining the prediction of postoperative morbidity and mortality using a comprehensive geriatric assessment reported a significantly higher risk for postoperative death or post-discharge institutionalization for orthopedic surgery compared with abdominal, thoracic, or other surgeries. As such, the value of a comprehensive geriatric assessment has been particularly recognized as a promising system of care for complex older patients who have suffered fragility fractures.
While frailty is increasingly acknowledged as a marker of functional decline, it remains a potentially modifiable risk factor. As such, preoperative rehabilitation programs have been introduced into clinical practice with the idea to reduce frailty and thereby improve surgical outcome. However, today the results of such prehabilitation programs remain controversial.
Neurologic Comorbidities
Stroke is a feared and devastating complication in the perioperative period and is associated with a high rate of morbidity and mortality. Large studies have identified a rate of 0.2% for perioperative stroke following total joint arthroplasty, the incidence doubling to 0.4% in patients aged 75 years or older. Mortazavi and associates reported advanced age, a history of cerebrovascular, coronary artery, atherosclerotic or cardiac valvular disease, atrial fibrillation or other intraoperative arrhythmias, urgent surgery, and general anesthesia as independent risk factors for stroke in patients undergoing total joint arthroplasties. Compared with matched control subjects not undergoing surgery, Lalmohamed and associates reported a 4.7-fold increased risk of ischemic stroke and a 4.4-fold increased risk for hemorrhagic stroke during the first 2 weeks after THA. The risk remained significantly elevated for at least 6 weeks for ischemic stroke and 12 weeks for hemorrhagic stroke. Since previous strokes represent a significant risk factor, a thorough evaluation of patients with neurologic diseases undergoing surgery can reduce perioperative morbidity and mortality.
Postoperative delirium is recognized as the most common surgical complication in older adults, occurring in 5% to 50% of older patients after surgery. It is associated with major postoperative complications, including postoperative cognitive dysfunction and even death. The main risk factors for postoperative delirium are well established and include among others age of 65 years or older chronic cognitive decline or dementia, poor vision or hearing, severe illness, and the presence of infection. In order to successfully prevent, predict, and manage postoperative delirium, different delirium risk scores were developed of which two were validated in orthopedic surgical patients. Kalisvaart and associates implemented and validated a medical risk factor model in 603 hip surgery patients aged 70 years or older containing four factors: cognitive function at admission, visual impairment, acute physiologic and chronic health status, and blood urea nitrogen (BUN) to creatinine ratio. One point was assigned for each of the four risk factors present, resulting in three groups: a low-, an intermediate-, and a high-risk group with incidences of delirium of 3.8%, 11.1%, and 37.1%, respectively. Cognitive impairment and age were the most important risk factors for delirium in this population of hip surgery patients. Postoperative delirium was four times as frequent in acute hip fracture patients as in elective hip replacement patients. Another study in elective hip or knee arthroplasty patients suggested the use of the Delirium Elderly At-Risk (DEAR) assessment, which incorporates the following risk factors: age, visual or hearing impairment, dependence in more than one activity of daily living, a low mini-mental state score on admission or a previous episode of postoperative delirium, and benzodiazepine or alcohol abuse. A score of two or more using this tool was associated with a greatly increased risk of delirium. Logistic regression models showed the strongest associations of substance abuse and cognitive impairment with the development of postoperative delirium. In a prospective matched controlled cohort study, Kat and colleagues showed that the risk of dementia or mild cognitive impairment at 30 months follow-up is almost doubled in hip surgery patients aged 70 years or older with postoperative delirium compared with at-risk patients without delirium. In addition, a recent study reported poor performance on a preoperative cognitive screening test in older patients undergoing hip or knee arthroplasties as a predictor of postoperative complications such as the development of postoperative delirium, a longer hospital stay, and a lower likelihood to return home in good health upon hospital discharge. Postoperative delirium is also common after spine surgery in older adults and is also associated with increased length of stay, increased costs, and decreased odds of discharge to home. All these studies clearly show the importance of incorporating the assessment of risk of delirium in the preoperative evaluation of elderly orthopedic patients.
Thromboembolic Disease
Thromboembolic complications remain one of the leading causes of morbidity and mortality after orthopedic surgery. Antithrombotic guidelines are continuously updated and published by the American College of Chest Physicians (ACCP). A systematic review and meta-analysis including 7 million pooled total joint arthroplasty patients found that cardiovascular disease, previous history of venous thromboembolism, neurologic disease, and ASA score were significant and independent risk factors for venous thromboembolism after joint arthroplasties. Two large studies published after the last update of the ACCP guidelines suggested aspirin to be an effective, safe, convenient, and inexpensive alternative to low-molecular weight heparin or to rivaroxaban for extended thromboprophylaxis after joint arthroplasties. In an evolving field with many new anticoagulation drugs available, accurate risk stratification would be helpful for physicians as well as patients. While the widely-used Caprini score risk assessment model for thromboembolic disease in the general surgical population failed to provide clinically useful risk stratification information in total joint arthroplasty patients, a more individualized risk model improved the efficacy of preventing venous thromboembolism in these patients. In spine surgery, venous thromboembolism prophylaxis remains even more controversial. An algorithmic approach to this problem was recently published to establish a more specific venous thromboembolism prophylaxis risk/benefit score for spinal surgery.
With the increased use of percutaneous coronary interventions and other vascular stents, and the widespread use of oral anticoagulant drugs for atrial fibrillation or peripheral vascular disease, anesthesiologists are commonly involved in the perioperative management of patients with antiplatelet or anticoagulation therapy. Moreover, a growing number of antiplatelet and anticoagulation therapies, including the non-vitamin K oral anticoagulants (novel or direct oral anticoagulants), with unique pharmacodynamic and pharmacokinetic properties complicates the perioperative management of these patients. The timing of discontinuation and postoperative restart of antithrombotic or anticoagulant therapy must be carefully planned and should always be evaluated against the risks of bleeding and cardiac events. An interdisciplinary approach to the perioperative coagulation management involving the surgeons, anesthesiologists, cardiologists, and hematologists may sometimes be required. Patient-specific factors (e.g., age, renal function, vascular and cardiac comorbidities) as well as the surgical factors (urgency, type, risk of bleeding) must be carefully evaluated for individualized risk assessment.
For this reason, we provide only a summary of current antiplatelet and anticoagulant drugs ( Tables 64.2 and 64.3 ). In general, arthroplasties are considered as having a moderate risk of bleeding, whereas vertebrospinal surgery is associated with a high risk of bleeding. In a brief and simplified summary for both types of operations, it is recommended that aspirin should be discontinued 5 days before surgery and until 7 days after surgery in patients with a low- to moderate cardiovascular risk (e.g., in patients taking aspirin as a primary prophylaxis). In patients with a high cardiovascular risk (e.g., patients with known coronary artery disease but an acute coronary syndrome >12 months preoperatively, drug-eluting stent >6 months, bare-metal stent >1 month, cardiac bypass surgery >6 weeks), aspirin can be continued during arthroplasty surgery. However, additional antiplatelet drugs should be discontinued according to their pharmacology and the renal function of the patient. For vertebrospinal surgery, it is advised that both drugs of a dual antiplatelet therapy are adequately stopped. Elective orthopedic surgery is not recommended without optimization in patients with a very high cardiovascular risk (acute coronary syndrome <12 months preoperatively, drug-eluting stent <6 months, bare-metal stent <1 month, cardiac bypass surgery <6 weeks, cerebrovascular accident <4 weeks); such surgery should be delayed when possible.
| Aspirin | Clopidogrel | Prasugrel | Ticagrelor | Cangrelor | Abciximab | Eptifibatide | Tirofiban | |
|---|---|---|---|---|---|---|---|---|
| Route of administration | Oral once daily | Oral once daily, (iv under investigation) | Oral once daily | Oral twice daily | iv | iv | iv | iv |
| Bioavailability | 68% | 50% | 80% | 36% | ||||
| Plasma peak level | 30-40 min | 1 h | 30 min | 1.5 h | Seconds | Dose dependent | Dose dependent | Dose dependent |
| Time to plasma steady state | 2-8 h | 30 min-4 h | 30 min-2 h | Seconds | Initial bolus and continuous application | Initial bolus and continuous application 4-6 h | Initial bolus and continuous application 10 min | |
| Plasma half-life | 15-30 min | 8 h | 7 h | 7 h | 2-5 min | 10-15 min | 2.5 h | 2 h |
| Plasma protein-binding | Strong | Strong | Strong | Strong | ||||
| Time from last dose to offset | 7-10 days | 7-10 days | 7-10 days | 5 days | 60 min | 12 h | 2-4 h | 2-4 h |
| Reversibility of platelet inhibition | No | No | No | Yes | Yes | Yes | Yes | Yes |
| Recommended period of discontinuation prior to surgical intervention | 0-5 days | 7 days | 10 days | 7 days | 1-6 h | 48 h | 8 h | 8 h |
| Oral | Parenteral | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Warfarin | Dabigatran | Apixaban | Edoxaban | Rivaroxaban | UFH (sc/iv) | LMWH (sc) | Fondaparinux (sc) | Argatroban (iv) | Bivalirudin (iv) | |
| Mechanism of action | Vitamin K antagonist | Direct inhibition Ila | Direct inhibition Xa | Direct inhibition Xa | Direct inhibition Xa | Direct inhibition Xa=IIa | Direct inhibition Xa>IIa | Direct inhibition Xa | Direct inhibition Ila | Direct inhibition Ila |
| Bioavailability | 80% | 6% | 66% | 62% | 80% | 30% | 90% | 100% | 100% | 100% |
| Plasma half-life | 20-60 h | 12-14 h | 8-15 h | 10-14 h | 7-10 h | 1 h | 4 h | 17 h | 50 min | 24 min |
| Duration of action from last dose | 48-96 h | 48 h | 24 h | 24 h | 24 h | Dose dependant (sc) | Dose dependant | 48-96 h | 2-4 h | 1 h |
| Peak plasma level | Variable | 2 h | 2.5-4 h | 1-2 h | 1-3 h | 4 h (sc) | 3 h | 2 h | 0.25-2 h | |
| Elimination | Metabolism | 80% renal | 25% renal | 50% renal | 50% renal, 50% hepatic | Reticuloendothelial system | Hepatic metabolism, renal excretion 10% | Renal | 65% feces, 22% urine | 20% renal |
| Drug interaction | CYP2C9, CYP3A4, CYP1A2 | P-glycoprotein inhibitors | CYP3Y4, P-glycoprotein inhibitors | P-glycoprotein inhibitors | Strong CYP3A4 inhibitors or inducers and P-glycoprotein inhibitors | |||||
Similar to patients on antiplatelet therapy, the management of patients under direct oral anticoagulant drugs or vitamin K antagonists also requires consideration of the individual risk of thromboembolic events balanced against the bleeding risk of surgery. Appropriate use of direct oral anticoagulants is particularly important with respect to regional anesthesia in orthopedic patients. The recommendations of the timing of the preoperative interruption of such treatment is somewhat different in Europe ( Table 64.4A ) and the United States ( Table 64.4B ). More recently, the American Society of Regional Anesthesia and Pain Medicine (ASRA) in conjunction with the European Society of Anaesthesiology convened a Consensus Conference on Regional Anesthesia and Anticoagulation that updated the available data, representing the collective experience of recognized experts in the field of neuraxial anesthesia and anticoagulation. These guidelines provide a comprehensive summary of evidence-based reviews, but emphasize that the decision to perform spinal or epidural anesthesia and the timing of catheter removal in a patient receiving antithrombotic therapy should be made on an individual basis, weighing the risks of spinal hematoma with the benefits of regional anesthesia for each individual.
| eGFR (mL/min) | Bleeding Risk Low to Moderate (h) | Bleeding Risk High (h) | |
|---|---|---|---|
| Dabigatran | ≥50 30-50 <30 | ≥24 48 ≥72 | 48 72 ≥120 |
| Factor Xa-inhibitors (rivaroxaban, apixaban, edoxaban) | ≥30 <30 | ≥24 ≥72 | 48 ≥72 |
| Direct Thrombin Inhibitor | Factor Xa Inhibitors | ||||
|---|---|---|---|---|---|
| Creatinine Clearance (mL/min) | Bleeding Risk Low | Bleeding Risk High | Bleeding Risk Low | Bleeding Risk High | |
| >80 | ≥1 day | ≥2-3 days | ≥1 day | ≥2 days | |
| 50-80 | ≥1-2 days | ≥3-4 days | ≥2-3 days | ||
| 30-49 | ≥4 days | ≥3-4 days | |||
| 15-29 | N/A | N/A | ≥36 h | ≥4 days | |
Pulmonary, Renal, Hematologic, Endocrine Diseases, and Nutritional Status
While cardiac diseases may be the most important considerations determining the overall outcome in high-risk orthopedic patients, other comorbidities such as pulmonary, renal, hematologic, endocrine, and nutritional diseases must also be examined during the preoperative evaluation of orthopedic patients. Although many studies examined postoperative pulmonary complications after noncardiothoracic surgery, they mainly focused on vascular, abdominal, or general surgical patients, and few studies focused on orthopedic surgery cases. In one such orthopedic study, patients suffering from chronic obstructive pulmonary disease who underwent total hip replacement were found to have a longer hospital length of stay, were more likely to be discharged to an extended-care facility, and were at a significantly increased risk for any other complication such as mortality, myocardial infarction, pneumonia, and septic shock. Another study in patients undergoing hip or knee replacements also reported a higher postoperative complication rate in patients with obstructive sleep apnea. In addition, since spine surgery in the prone position is accompanied by a decreased respiratory compliance, patients after major spine surgery are at increased risk of postoperative pulmonary complications. Therefore, a thorough pulmonary evaluation and physical examination, including a detailed history, and subsequent medical optimization are critical steps in the preoperative management of orthopedic patients. In selected patients, additional investigations such as chest radiography, spirometry, and assessments of arterial blood gases, albumin levels (OR for pulmonary complications of 2.53 with an albumin level <3.5 g/dL), and BUN (OR 4.81 with a BUN level >7.5 mmol/L) should be considered. In patients scheduled for major scoliosis operations, preoperative fluoroscopy or magnetic resonance imaging to evaluate diaphragm and chest wall movements and preoperative pulmonary function testing might be indicated. The risk of postoperative pulmonary complications can also be estimated with easy-to-use risk scores. A strong body of evidence suggests that lung expansion therapy, such as incentive spirometry or deep breathing exercises, can reduce postoperative pulmonary risk.
Today, with medical advancements leading to improved survival and function, an increasing number of patients with chronic kidney disease present for elective orthopedic surgery. There is some discrepancy in the literature with respect to outcome of elective orthopedic surgery in patients with end-stage renal disease (ESRD). Two large retrospective studies failed to show an increased incidence of surgical site infections, thromboembolic events, and 90-day mortality in patients with ESRD undergoing hip replacement surgery. Other investigators found higher rates of postoperative complications such as cardiovascular, pulmonary, infectious, and thromboembolic events as well as an increased readmission and mortality rate in patients with ESRD who underwent joint replacement surgery. The main concerns for the anesthesiologist in these patients include timing of preoperative and postoperative dialysis to avoid hypervolemia, hyperkalemia, and acidosis; cardiovascular assessment and blood pressure control; electrolyte management, anemia, drug metabolism, and the balance between thromboembolic complications and higher bleeding risk, both of which can be increased in patients with ESRD. The pathophysiology of bone disease represents another important factor to consider preoperatively, since both low and high abnormal bone turnover contribute to the poor bone strength in these patients. Poor bone quality could lead to challenging surgical conditions requiring the use of locking plates or screws, cement fixation, and less rigorous postoperative ambulation, all of which potentially contribute to an increased rate of postoperative complications.
The overall incidence of anemia in the general population increases with age and is estimated to be 10% to 11% in the older adult aged 65 years or older. Until recently, anemia in older adults was often viewed simply as an abnormal laboratory test value with limited consequences. But today, substantial evidence in the literature reveals that previously undiagnosed anemia is common in elective orthopedic patients, and importantly is associated with increased likelihood of blood transfusion and increased perioperative morbidity and mortality. The preoperative evaluation of anemia should, therefore, include considerations to optimize the endogenous red blood cell mass through targeted stimulation of erythropoiesis and treatment of modifiable underlying disorders. Efforts should be made to diagnose and start appropriate treatment of preoperative anemia and minimize perioperative blood loss. This can be achieved through vigilant adherence to protocols including the measurement of hemoglobin, serum ferritin, transferrin saturation, transferrin receptor index, reticulocyte hemoglobin, vitamin B 12 , folic acid, serum creatinine, and glomerular filtration rate starting as early as 28 days before surgery ( Fig. 64.4 ). Implementation of such anemia prevention and management in elective orthopedic patients can improve patient safety and outcomes. The preoperative administration of iron carboxymaltose in anemic patients undergoing major orthopedic surgery resulted in a significant decrease in postoperative infectious complications from 12.0% to 7.9%. Moreover, hospital length of stay was shortened by 1 day.
In addition to the well-recognized risks of antiplatelet and anticoagulant therapy discussed earlier, some orthopedic patients present with impaired primary hemostasis. Since the management of impaired primary hemostasis is no different in orthopedic surgery than in other surgical fields with associated bleeding risks, such as neurosurgery, we will only briefly summarize here some relevant ideas. Based on robust evidence in the literature, it is recommended that patients with an increased risk of bleeding complications are identified using a standardized questionnaire and, only if indicated, the measurement of platelet count, prothrombin time, activated partial thromboplastin time, PFA-100 platelet function analyzer test, and von Willebrand factor ( Table 64.5 ).
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Finally, endocrine and nutritional aspects also have an impact on outcome in orthopedic surgery. For severely obese patients, spine surgery is associated with decreased quality of preoperative and intraoperative imaging, surgical limitations due to inadequate operative exposure, increased anesthetic risk such as esophageal reflux and ventilation-perfusion mismatches, and an increased risk of perioperative complications such as wound infection, increased blood loss, venous thrombosis, pneumonia, and nerve injuries as a result of positioning difficulties. Conversely, malnutrition is also associated with increased pulmonary risk, increased risk of surgical site infection, and poor surgical outcomes both in spinal and arthroplastic surgery. Screening for malnutrition in orthopedic surgery includes the measurement of body mass index, anthropometric measurements such as calf or arm muscle circumference, and triceps skinfold, and the determination of serologic laboratory values such as total lymphocyte count (<1500 cells/mm 3 ), serum albumin (<3.5 g/dL), prealbumin (<16 mg/dL), transferrin (<200 mg/dL), and zinc levels (<66-95 μg/dL). Various scoring systems have been used to detect malnutrition in orthopedic surgery. The Mini Nutritional Assessment is a simple and effective tool for identifying patients at severe nutritional risk. While routine enteral or parenteral nutrition does not reduce perioperative risks, patients with severe malnutrition should undergo nutritional assessment by a dietician prior to surgery. The risks and benefits of delaying elective surgery until the nutritional status has improved should be discussed with the patient. Similarly, delaying elective orthopedic surgery in patients with diabetes mellitus with an increased level of hemoglobin A 1C (>7%) until after a better glycemic control has been obtained may reduce risk of surgical wound infection and improve outcome.
Complications and Outcome
A very interesting study in more than 100,000 patients identified the determinants of 30-day postoperative mortality and long-term survival after major surgery exemplified by eight common operations, one being total hip replacement. These authors found in a sample size of 12,184 patients undergoing total hip replacement a 30-day mortality rate of 1% and a mortality rate at any time during an average follow-up time of 8 years of 20%, compared with a 30-day mortality rate of 3% and 36% during the 8-year follow up in the whole study population. After a 10-year follow up, the survival rate in the hip replacement surgery patients was still almost 75%. The main complications in hip replacement surgery were urinary tract infection, deep vein thrombosis (DVT), pneumonia, superficial wound infection, deep wound infection, prosthesis failure, pulmonary embolism, myocardial infarction, and peripheral nerve injury. With the presence of any of these complications, the 30-day mortality rate increased from 1% to 6.4%. The occurrence of a postoperative pneumonia increased the 30-day mortality rate to 16.4% and the 5-year mortality rate to 62.7%, and the occurrence of a perioperative myocardial infarction increased the 30-day mortality rate to 29.2% and the 5-year mortality rate to 52.1%. Given these high numbers of adverse outcomes after the occurrence of complications in total joint arthroplasty patients, every effort must be made during the preoperative evaluation to detect patients at risk, to treat potential underlying conditions, and to optimize the health status of patients. Preoperative medical assessment is an important part of the surgical plan. Identifying and treating modifiable risk factors in the preoperative setting can decrease the risk of surgical complications. A standard protocol that involves a multidisciplinary approach to patients in the preoperative, operative, and postoperative periods may ultimately lead to better outcomes and reduced costs.
Special Considerations for Conditions Leading to Orthopedic Surgery
Osteoarthritis
OA is a degenerative joint disease characterized by articular cartilage loss and osteophyte formation, most often in the hands, knees, hips, feet, and spine. Symptoms include joint pain, which is typically worse with activity, and decreased range of motion. OA is one of the most common causes of chronic pain and disability among older individuals and is the most common reason that patients present for total knee and hip replacement surgery (USBJI). After age, the most important risk factors for OA include obesity and joint trauma or malalignment.
Although OA has no systemic manifestations, medical comorbidities such as cardiac disease and diabetes are common in these patients, and the combination of OA with one of these chronic conditions is associated with a greater degree of physical activity limitation. Preoperative evaluation should take this into account. Patients with chronic pain related to OA, especially those with chronic opioid use, may benefit from a multimodal perioperative analgesic regimen. Patients who frequently take nonsteroidal antiinflammatory drugs (NSAIDs) should be questioned about symptoms of peptic ulcer disease and gastroesophageal reflux. Extra care should be taken when positioning these patients for surgery, being mindful of painful, stiff joints, and existing orthopedic hardware. Severe OA of the cervical spine may affect airway management, whereas severe disease of the thoracic or lumbar spine may make neuraxial techniques more challenging.
Rheumatoid Arthritis
Rheumatoid arthritis (RA) is an autoimmune inflammatory disease that affects the joints and often other organ systems. It affects approximately 1% of the population in developed nations, is twice as common in women as in men, and most often presents between 60 and 80 years of age. Most patients have detectable autoantibodies such as rheumatoid factor and anticitrullinated protein antibody. Articular manifestations include synovial inflammation and hypertrophy and destruction of cartilage and bone. This presents clinically as painful joint swelling, stiffness, and progressive deformity. In contrast to OA, the pain and stiffness of RA are typically worse after periods of rest and improve with activity. RA most commonly affects the small joints of the hands and feet in a symmetric fashion but may progress to involve larger joints and atypical joints such as the temporomandibular and cricoarytenoid joints. Cervical spine involvement occurs in up to 80% of RA patients. Because RA is a systemic disease, anesthetic considerations can be complex ( Table 64.6 ).
| Airway | Limited TMJ movement Narrow glottis opening |
| Cervical spine | Atlantoaxial instability |
| Cardiac | Pericarditis Pericardial fluid with tamponade physiology |
| Eyes | Sjögren syndrome |
| Gastrointestinal | Gastric ulcers secondary to ASA or steroids |
| Pulmonary | Diffuse interstitial fibrosis |
| Renal | Renal insufficiency secondary to NSAIDs |
Similar to patients with OA, patients with RA require careful attention to positioning for surgery, especially if cervical spine disease is suspected. Cervical instability is common in RA, affecting up to 61% of RA patients undergoing elective total joint replacement in one study. Instability may result from atlantoaxial or subaxial subluxation, and places the patient at risk for spinal cord compression if the neck is malpositioned ( Fig. 64.5 ). No guidelines exist for preoperative cervical spine evaluation in RA patients. Certainly, patients should be questioned about neck range of motion and any symptoms of pain or radiculopathy. However, significant cervical disease may exist in the absence of symptoms. Radiography of the cervical spine may be considered, and if obtained should include lateral views in flexion and extension, frontal view of the entire cervical spine, and frontal open-mouth odontoid view. If the distance between the posterior border of the odontoid process and the anterior aspect of the posterior arch of C1 is less than 14 mm, a degree of spinal cord compression is likely present ( Fig. 64.6 ).
If cervical instability is suspected, airway management should proceed cautiously with minimal manipulation of the neck. Even in the absence of cervical spine disease, patients with RA may present with challenging airways due to temporomandibular joint disease that limits mouth opening or cricoarytenoid joint stiffness that impedes passage of the endotracheal tube. Fiberoptic intubation or regional techniques with a natural airway may be attractive options for these patients.
Extraarticular manifestations of RA are common and are associated with increased morbidity and mortality, primarily related to cardiovascular disease. The systemic inflammation caused by RA contributes to premature atherosclerosis. As a result, the risk of myocardial infarction, congestive heart failure, and stroke is twice as high in patients with RA compared to individuals without RA. Pericarditis is the most common cardiac manifestation of RA but rarely results in clinically significant disease. Although RA has not been shown to be an independent risk factor for perioperative mortality or adverse cardiovascular events, thorough preoperative cardiovascular risk assessment is warranted in these patients. Pulmonary involvement of RA is also relatively common in the form of pleural effusions and interstitial lung disease. Severity varies from subclinical to, rarely, severe. Preoperative chest radiography or pulmonary function tests may be informative when significant pulmonary disease is suspected. Other extraarticular manifestations of RA include subcutaneous rheumatoid nodules on bony prominences or extensor surfaces, small- to medium-vessel vasculitis, and hematologic abnormalities such as anemia and thrombocytosis.
Treatment for RA focuses on early initiation of disease-modifying antirheumatic drug (DMARD) therapy, with the goal of achieving clinical and radiographic disease remission. In addition to conventional DMARDs such as methotrexate, hydroxychloroquine, sulfasalazine, and leflunomide, many patients benefit from treatment with an ever-growing arsenal of biologic agents that use monoclonal antibodies or receptor proteins to inhibit inflammatory cytokines or cell lines. A notable risk with DMARDs is immunosuppression and possibly impaired wound healing. Current evidence supports continuation of methotrexate perioperatively but is inconclusive about the effect of other agents on perioperative infection and wound complication rates. A conservative approach is to hold biologic agents for at least one dosage cycle prior to surgery and resume once wound healing has progressed. In each case, the benefit of improved immune function and wound healing must be balanced with the risk of disease flare, and it may be appropriate to continue DMARDs perioperatively for some patients. This plan should be developed with input from the patient’s rheumatologist and surgeon. Patients taking corticosteroids for RA may require stress-dose steroids perioperatively. They should be questioned about symptoms of gastroesophageal reflux, as should patients who take NSAIDs chronically.
Ankylosing Spondylitis
Ankylosing spondylitis is an autoimmune seronegative spondyloarthropathy that typically affects the spine and sacroiliac joints but may involve peripheral joints as well. It affects men disproportionately and most often presents between the ages of 20 to 30 years. Inflammation in affected joints leads to formation of fibrocartilage and ectopic bone, and ultimately fusion of the joint. The classic “bamboo spine” appearance seen radiographically in advanced disease is caused by ossification of the vertebral ligaments. This in combination with osteoporotic compression fractures can result in rigid kyphosis that may require surgical correction ( Fig. 64.7 ).
Despite their rigidity, the spines of patients with advanced ankylosing spondylitis are also quite fragile. Vertebral fractures may occur spontaneously or with minimal trauma; the cervical spine is a common site. Obviously, this has serious implications for intraoperative positioning and airway management. Neck range of motion and preexisting neurologic deficits should be thoroughly evaluated preoperatively, and adequate neck support must be provided at all times to avoid hyperextension. Cervical kyphosis may make direct laryngoscopy difficult or impossible, and temporomandibular joint disease may limit mouth opening. Awake fiberoptic intubation may be the safest option in patients with severe cervical disease, as it allows for spontaneous ventilation as well as neurologic monitoring throughout intubation. Video laryngoscopy has also been used successfully in ankylosing spondylitis patients. The laryngeal mask airway (LMA) may be useful in cases where endotracheal intubation is not required, or as a bridge to intubation if an intubating LMA is used.
The spinal pathology of ankylosing spondylitis may also result in difficulty with neuraxial techniques. Furthermore, the incidence of epidural hematoma after neuraxial anesthesia is higher in ankylosing spondylitis patients than in the general population. This may be related to an increased incidence of traumatic needle placement, the prevalence of NSAID use among ankylosing spondylitis patients, or narrowing of the epidural space that makes symptomatic spinal cord compression more likely when a hematoma occurs. If neuraxial anesthesia is indicated, ultrasound or fluoroscopic guidance may facilitate placement. Subsequently, vigilance should be maintained for symptoms of epidural hematoma.
Extraarticular manifestations of ankylosing spondylitis occur more often in patients with severe disease. Inflammation and fibrosis of the ascending aorta and aortic root can lead to aortic insufficiency, and extension to the conduction system may result in heart block or supraventricular arrhythmias. The prevalence of aortic insufficiency and conduction abnormalities in ankylosing spondylitis patients increases with duration of disease, occurring in 3.5% and 2.7%, respectively, after 15 years and 10% and 8.5%, respectively, after 30 years. As in RA, patients with ankylosing spondylitis also have an elevated risk of atherosclerosis. Pulmonary manifestations of ankylosing spondylitis include restrictive lung disease due to kyphosis and chest wall rigidity. Pulmonary fibrosis may be seen in advanced disease. The duration and severity of disease should inform the extent of preoperative cardiopulmonary evaluation, which might include electrocardiography, echocardiography, and/or pulmonary function testing.
Achondroplasia
Achondroplasia is characterized by disproportionately short stature, lumbar lordosis, large head, midface hypoplasia, short hands, and normal cognitive development. Its incidence is estimated at 1 in 10,000 to 1 in 30,000. Although it is an autosomal-dominant condition, the majority of cases occur as a result of a de novo genetic mutation. Patients with achondroplasia may present for orthopedic surgery as children or adults for correction of associated abnormalities such as tibial bowing and spinal stenosis.
The primary anesthetic challenge in patients with achondroplasia is airway management. Midface hypoplasia with a pharynx that is small in proportion to the tonsils, adenoids, and tongue makes these patients prone to upper airway obstruction and may hinder direct laryngoscopy. A flat nasal bridge and large mandible may make it difficult to obtain an adequate seal for mask ventilation. Hyperextension of the neck should be avoided due to the possibility of foramen magnum stenosis. Video laryngoscopy or fiberoptic intubation should be considered for these patients, and a range of endotracheal tube sizes should be on hand, as many patients require a size smaller than what would be expected based on age. Other anesthetic considerations in patients with achondroplasia include the possibility of difficult neuraxial anesthesia due to spinal deformity or stenosis, and cardiopulmonary sequelae such as restrictive lung disease, central and obstructive sleep apnea, and resultant pulmonary hypertension. Preoperative echocardiogram to assess for pulmonary hypertension should be considered prior to major surgery.
Orthopedic Procedures in Children with Special Conditions
The anesthetic management of children undergoing orthopedic surgery is beyond the scope of this chapter. However, a number of musculoskeletal conditions will require multiple orthopedic surgeries during childhood and may pose special challenges to the anesthesiologist.
Juvenile Idiopathic Arthritis
Juvenile idiopathic arthritis (JIA) is the most common rheumatic disease in children. It is characterized by chronic arthritis with onset before the age of 16 and encompasses five distinct subtypes as described below. JIA may be seropositive or seronegative, is twice as common in girls as in boys, and may persist into adulthood.
- 1.
Oligoarticular JIA: Involves fewer than 5 joints. Accounts for at least 50% of JIA. Often has an indolent presentation.
- 2.
Polyarticular JIA: Involves 5 or more joints. Accounts for 25% to 40% of JIA. Usually requires DMARD therapy.
- 3.
Psoriatic JIA: Arthritis with psoriasis.
- 4.
Enthesitis-related JIA: Affects the spine, sacroiliac joints, and points of tendon attachment to bone.
- 5.
Systemic-onset JIA: Presents with daily fever and rash.
As in adult arthritis, special care should be paid to joint range of motion and intraoperative positioning for patients with JIA. The cervical spine and temporomandibular joints may be affected in JIA, especially in the polyarticular subtype, and appropriate precautions should be taken when planning for airway management. In children, awake fiberoptic intubation may not be a feasible option. In this case, fiberoptic intubation may be performed asleep with spontaneous ventilation maintained throughout induction. Common extraarticular manifestations of JIA include growth abnormalities and uveitis. Pericarditis and pleural effusions sometimes occur in systemic-onset JIA. Medical therapies for JIA are similar to those for RA, including conventional DMARDs and biologics, which raise similar considerations for perioperative risks and management.
Osteogenesis Imperfecta
Osteogenesis imperfecta encompasses a group of heritable bone dysplasias caused by mutations in collagen-related genes. It occurs with an incidence of 1 in 10,000 and is characterized by bone fragility resulting in deformity and susceptibility to fracture. Secondary features include short stature, blue or gray sclerae, conductive hearing loss, abnormal dentin resulting in weak and discolored teeth, foramen magnum stenosis, cardiac valvular abnormalities, and bleeding diathesis. Although the most severe subtype of osteogenesis imperfecta results in perinatal death, the life expectancy for patients with other subtypes extends well into adulthood.
Patients with osteogenesis imperfecta may require a number of orthopedic surgeries such as fracture fixation, intramedullary rodding for correction of long-bone deformities, spinal fusion for scoliosis, and joint replacement. Anesthetic management may be challenging ( Table 64.7 ). Utmost care must be taken to avoid iatrogenic fracture when positioning these patients for surgery. The area under the blood pressure cuff should be padded or an arterial line placed to minimize the risk of humeral fracture. Tourniquets must be managed with similar care. Succinylcholine should be avoided in patients with osteogenesis imperfecta because of the risk of fracture upon fasciculation. Airway management must be performed gently with minimal manipulation of the head and neck to avoid cervical, facial, and dental fractures. Fiberoptic intubation may facilitate this. Neuraxial techniques may be considered in patients with normal platelet function but may be challenging due to scoliosis. Care must be taken to avoid needle trauma to bone and intraosseous injection.
| Airway | Risk for fractures of the mandible, maxillary surface, and cervical spine |
| Bleeding | Platelet abnormalities |
| Cardiac | Congenital and valvular heart disease Cystic degeneration of proximal aorta |
| Eyes | Exophthalmos Risks associated with prone positioning |
| Hyperthermia | Malignant hyperthermia, hydration, possible cooling |
| Positioning | Risk for fractures |
| Pulmonary | Kyphoscoliosis, restrictive lung disease |
| Regional anesthesia | Fractures, intraosseous injections |
Several extraskeletal manifestations of osteogenesis imperfecta are relevant to the anesthesiologist. The same collagen abnormalities that affect bone may also affect the cardiac valves and aorta, resulting in regurgitant lesions, aortic root dilation, and even aortic dissection. Restrictive or obstructive lung disease may be present as a result of kyphoscoliosis or chest wall deformity. In fact, pulmonary complications are the leading cause of death in osteogenesis imperfecta. Preoperative echocardiography or pulmonary function testing should be considered if a murmur or symptoms of cardiopulmonary disease are noted. Patients with osteogenesis imperfecta are at risk for increased surgical bleeding due to platelet dysfunction and vessel fragility. Patients should be evaluated for coagulopathy preoperatively, and if necessary, treated with desmopressin (DDAVP) or platelet transfusion.
A link between osteogenesis imperfecta and malignant hyperthermia (MH) has been suggested in the literature, but the evidence for this association is weak. Intraoperative hyperthermia and metabolic acidosis have been observed in patients with osteogenesis imperfecta, but in most cases, this was not associated with other signs of hypermetabolism and resolved with cooling measures alone. There is a lack of consensus on the use of MH-triggering agents in patients with osteogenesis imperfecta. The most conservative approach is to administer a nontriggering anesthetic, but in cases where this presents a significant challenge (as in an uncooperative child with difficult intravenous access), use of volatile anesthetics may be considered. In all cases, patients should be carefully monitored for hyperthermia and acidosis, and appropriate treatment modalities should be readily available.
Cerebral Palsy
Cerebral palsy is the most prevalent cause of persistent motor impairment in children, affecting 1 to 2 of every 1000 live births in developed countries. It is caused by antenatal or perinatal injury to the developing brain and is characterized by nonprogressive abnormalities of movement and posture such as spasticity, ataxia, and dyskinesias. The motor deficit may be mild or severe, isolated, or accompanied by other abnormalities including cognitive impairment, speech disorders, and seizures. Patients with cerebral palsy often require multiple orthopedic surgeries such as soft tissue release and tendon lengthening for contractures, osteotomies for hip deformities, and spinal fusion for scoliosis.
Anesthetic management of patients with cerebral palsy requires consideration of the psychosocial as well as medical aspects of their condition. Communication may be challenging due to cognitive delay, behavioral problems, or speech difficulties, necessitating special accommodations and involvement of parents or caretakers in perioperative interactions. It is important to remember that speech impairment does not necessarily imply cognitive impairment. In patients with seizures, antiepileptic drugs should be continued perioperatively and inquiry made as to the frequency and semiology of seizures. Gastroesophageal reflux is common in cerebral palsy and may be an indication for rapid sequence intubation. Bulbar dysfunction can further contribute to chronic aspiration and feeding difficulties that sometimes requires gastrostomy tube placement. Chronic aspiration, recurrent respiratory infections, and restrictive deficits due to kyphoscoliosis result in significant pulmonary morbidity in these patients. Airway management may be challenging due to cervical kyphosis or dystonia, temporomandibular joint dysfunction, or poor dentition. Patients with cerebral palsy have a lower minimum alveolar concentration (MAC) than normal controls and may be prone to intraoperative hypothermia due to hypothalamic dysfunction. An association between cerebral palsy and latex allergy has been noted, likely related to the multiple surgical procedures many of these patients undergo.
Spina Bifida
Spina bifida is a term that is broadly applied to a diverse group of congenital malformations of the spine and spinal cord. Embryologically, these conditions result from a failure of fusion of the neural tube. Discussion of spina bifida is complicated by a lack of consistency in terminology and classification, but malformations can be broadly divided into open defects with exposed neural tissue such as myelomeningocele and myeloschisis, and closed defects with a skin covering such as meningocele, tethered cord, and split cord. Open defects are usually associated with a neurologic deficit and are almost always repaired perinatally, or with the advent of fetal surgery, prenatally. Closed defects may have an associated deficit or may be asymptomatic and undiagnosed until adulthood. Cutaneous abnormalities such as a sacral dimple, hemangioma, or tuft of hair may raise suspicion for a closed defect, but these are not always present.
Neurologic abnormalities associated with spina bifida include motor and sensory deficits below the level of the defect, Chiari II malformation, hydrocephalus, and neurogenic bladder. Patients with spina bifida may present for orthopedic surgery for correction of congenital or acquired limb deformities such as clubfoot or hip dislocation, spinal fusion for scoliosis, or release of contractures. Patients with tethered cord syndrome may present for cord release as children or adults. As in cerebral palsy, repeated surgical exposures in spina bifida patients result in an increased incidence of latex allergy.
The most significant anesthetic implications of spina bifida are related to neuraxial anesthesia. Whether or not the patient has undergone corrective spinal surgery, anatomic abnormalities in the spine can lead to an increased risk of inadvertent dural puncture, failed block, and neurologic injury. For example, the ligamentum flavum may be malformed or absent, precluding identification of the epidural space with loss-of-resistance technique. The epidural space may be abnormal or nonexistent in patients who have undergone prior surgical repair. Cord tethering can result in low termination of the spinal cord and posterior placement of neural elements within the spinal canal, increasing the risk of neurologic injury with spinal anesthesia or inadvertent dural puncture. Neuraxial techniques should be approached with extreme caution in patients with tethered cord syndrome, if at all.
If neuraxial anesthesia is indicated in a patient with spina bifida, it should only be attempted if there is a thorough understanding of the patient’s spinal anatomy. Magnetic resonance imaging (MRI) of the spine should be obtained to allow for examination of bony and ligamentous defects, the level of termination of the spinal cord, and the presence of masses such as lipoma or syrinx. Needle placement through surgical scars should be avoided, and epidurals should be placed above the level of the spinal defect. Smaller than usual epidural boluses are recommended, as abnormal anatomy might result in more extensive spread. Failed or incomplete block may result in the need for rescue analgesia or conversion to general anesthesia.
Duchenne Muscular Dystrophy
Duchenne muscular dystrophy (DMD) is an X-linked recessive neuromuscular disorder that occurs in 16 per 100,000 live male births in the United States. Mutations in the dystrophin gene result in muscular degeneration that is progressive and ultimately fatal. Weakness usually begins in early childhood with loss of ambulation by age 8 to 12 years, respiratory insufficiency and cardiomyopathy by the early 20s, and death before age 30 due to pulmonary complications or heart failure. However, with advancements in care, the life expectancy for DMD is improving, and some patients may survive into their 30s or 40s. Glucocorticoids are the mainstay of treatment for DMD. Patients with DMD may present for orthopedic surgery to correct lower extremity deformity, scoliosis, or contractures. These patients are also prone to osteoporosis with increased risk of fractures that may require operative fixation.
Patients with DMD have an elevated risk of perioperative cardiac and respiratory decompensation and should undergo a thorough cardiopulmonary evaluation prior to surgery. Depending on the stage of their disease, this may include an electrocardiogram, echocardiogram, and pulmonary function testing. Extubation to noninvasive positive pressure ventilation is recommended for patients with a forced vital capacity (FVC) less than 50% predicted, and essential for those with an FVC less than 30% predicted. Aggressive postoperative pulmonary hygiene should be strongly encouraged.
Use of succinylcholine is strictly contraindicated in patients with DMD because of the risk of acute rhabdomyolysis. Inhaled anesthetics are also best avoided, as they have been implicated in cases of perioperative metabolic reactions ranging from intraoperative hyperthermia and tachycardia to rhabdomyolysis to hyperkalemic arrest. The mechanism of these reactions is thought to be distinct from that of MH. Patients with DMD have both a delayed onset time and prolonged recovery time with nondepolarizing neuromuscular blockers, which places them at risk for residual neuromuscular blockade and recurarization. Quantitative monitoring of neuromuscular blockade is recommended to ensure full reversal. Cholinesterase inhibitors are safe and effective for reversal in these patients, and sugammadex has been used successfully as well.
Arthrogryposis Multiplex Congenita
Arthrogryposis multiplex congenita is characterized by congenital nonprogressive contractures affecting at least two different areas of the body. It occurs with an incidence of about 1 in 4300 to 5100 live births. Arthrogryposis multiplex congenita is not a single disorder, as once thought, but actually encompasses hundreds of conditions with distinct etiologies, both genetic and environmental. A common theme in most of these is decreased fetal movement, which leads to abnormal joint development. Deformity may be limited to the limbs or associated with spine and craniofacial abnormalities. Neurologic dysfunction is present in some cases and portends a less favorable prognosis.
Treatment of arthrogryposis multiplex congenita requires early orthopedic intervention with splinting and surgery to optimize a child’s ability to ambulate and perform activities of daily living. The primary anesthetic challenge in arthrogryposis multiplex congenita is airway management, which may be complicated by craniofacial abnormalities such as small mouth opening, high arched palate, or micrognathia, as well as limited cervical range of motion. These patients are at risk of perioperative respiratory complications as a result of restrictive thoracic deformities and increased sensitivity to opioids and neuromuscular blockers. This makes regional and neuraxial anesthesia attractive options, but these techniques may be challenging due to limb contractures, scoliosis, or associated spina bifida.
Two cases of suspected MH have been reported in patients with arthrogryposis multiplex congenita, as well as other cases of perioperative hyperthermia and hypermetabolism without skeletal muscle destruction. As such, succinylcholine should be avoided in these patients, and exposure to volatile anesthetics should be minimized.
Perioperative Management of the Orthopedic Patient
Special Considerations
In addition to the perioperative cardiovascular, pulmonary, renal, and hepatic considerations described earlier, orthopedic procedures are associated with unique risks and complications related to bone injury, immobilization, and the use of implants and cement material. Bone hemostasis can be difficult, and without antifibrinolytic agents, even primary hip and knee arthroplasties can be associated with considerable bleeding requiring transfusion of blood products. Extensive review of these considerations is beyond the scope of this chapter, but given the rising interest in the literature and its clinical importance, perioperative use of antifibrinolytic agents is summarized below, along with the clinical presentation and management of fat embolism and bone cement implantation syndrome.
Antifibrinolytic Drugs
Blood transfusions are associated with an increased risk of adverse events including mortality, prolonged length of hospitalization, and higher overall costs associated with surgery. Antifibrinolytic agents, such as tranexamic acid (TXA) and epsilon-aminocaproic acid (EACA), bind reversibly to plasminogen by its lysin-binding site, inhibiting its association with fibrin. They also inhibit the proteolytic activity of plasmin. Both TXA and EACA are effective in reducing perioperative blood loss and the need for transfusion and reoperation for bleeding.
Among orthopedic surgeries, the strongest evidence for the use of TXA and EACA is found in multilevel spine surgeries and arthroplasties. Several comprehensive meta-analyses have examined the use of systemic TXA in these procedures. Two meta-analyses studying the use of intravenous TXA in spine surgeries demonstrated significant reductions in intraoperative and postoperative blood loss and allogenic blood transfusion compared with placebo. However, initiation doses (10-20 mg/kg, 100 mg/kg, or 1-2 g) and maintenance doses (1 mg/kg/h, 10 mg/kg/h, and 100 mg/kg/h) were highly variable. Similar results with regard to efficacy and safety have been shown with the use of intravenous TXA in TKA and THA. TXA has been shown to reduce total blood loss, postoperative bleeding, and the transfusion rate when given intraoperatively with an intravenous infusion compared to a postoperative administration. A common approach is to administer 10 to 15 mg/kg before the incision, followed by a 1 mg/kg/h infusion during the surgery. A recent meta-analysis also demonstrated that TXA resulted in significant reductions in total blood loss and transfusion requirements following total shoulder arthroplasty. The rate of thromboembolic events was not significantly greater when the above dose of TXA was administered in selective patients without contraindications.
Topical administration of TXA, although not a US Food and Drug Administration (FDA)-approved route of administration, has a theoretical safety benefit over intravenous administration. Topical TXA has shown superior efficacy to placebo and similar efficacy (measured as reductions in total blood loss and transfusion rates) to intravenous TXA in TKA and THA. No difference in the rate of thromboembolic events has been demonstrated when comparing topical TXA to placebo or intravenous TXA. The doses of topical TXA used in studies are highly variable and usually range from 1 to 3 g. Thus, a standard topical dose has not yet been established.
EACA has also been shown to decrease total blood loss and need for transfusion among patients undergoing spine surgeries. Among TKA and THA patients, however, EACA did not reduce the need for blood transfusion. An increased risk of DVT and pulmonary embolism has not been reported following the use of EACA in THA, though sufficient data in TKA or spine surgeries are not yet available. Loading doses (100-150 mg/kg or 5 g) with a continuous infusion ranging from 10 to 15 mg/kg/h during spine surgeries have been used. For THA and TKA, weight-based (12.5-100 mg/kg) and fixed doses (5-10 g) of EACA have been utilized.
Although no increase in the incidence of venous thromboembolism was observed in the above randomized clinical trials, it is important to note that high-risk patients were excluded and none of the studies was adequately powered to detect smaller but clinically relevant differences between treatment groups. Therefore, because of concerns of venous thromboembolism, antifibrinolytic agents are commonly avoided in patients who have any of the following conditions: a history of arterial or venous thromboembolic disease; a recent placement of a cardiac stent; a history of severe ischemic heart disease (NYHA Class III or IV) or myocardial infarction; and history of cerebrovascular accident, renal impairment, or pregnancy. Currently, there is limited data to support the use of EACA in spine surgeries, THA, or TKA, whereas evidence for TXA is more robust. In select patients who are at high risk for transfusion, intravenous or topical TXA should be considered.
Fat Embolism Syndrome
The subclinical form of fat embolism occurs in nearly all patients following long bone or pelvic fractures, as well as after hip or knee replacement surgeries. A clinically significant fat embolism syndrome (FES) is present in up to 30% of these patients. An increase in intramedullary pressure and a disruption of the venous sinusoids within the long bones following a fracture or a surgical manipulation such as reaming can result in fat and bone marrow debris entering the venous circulation. The debris lodges in the lung microvasculature, leading to a mechanical obstruction of pulmonary circulation. Free fatty acids released following hydrolysis of fat globules trigger systemic inflammatory response and induce injury to the pulmonary endothelium with an increased capillary leak and increased platelet adhesion with clot formation in the microvasculature. In the presence of intracardiac (patent foramen ovale) or pulmonary shunts, fat particles may also enter the systemic circulation leading to cerebral and cutaneous manifestations.
Symptoms of FES include hypoxemia, respiratory alkalosis, mental status changes, petechial rash (in the conjunctiva, oral mucosa, and skin folds of the neck and axilla), thrombocytopenia, and fat microglobulinemia. The presentation of FES can be gradual, developing between 12 and 72 hours after trauma or surgery. Intraoperatively, FES can also present as a cardiovascular collapse following reaming of long bones, intramedullary insertion of cemented prosthesis, or tourniquet release. Chest radiographs usually show bilateral diffuse infiltrates, particularly in the upper and middle lobes of the lung. MRI of the brain of the patients with significant mental status changes can reveal multiple hyperintensive lesions. Arterial blood gas assessment is useful to determine the degree of hypoxemia. The best preventive management strategy of FES is an early surgical reduction and immobilization of the fracture site. Therapy of FES includes early supportive care with supplemental oxygen and, if necessary, mechanical ventilation to correct hypoxemia, and careful fluid management to prevent worsening of capillary leak. There is currently no evidence supporting the use of steroids, heparin, or dextran in the management of FES. The overall mortality remains high (up to 20%).
Bone-Cement Implantation Syndrome
During arthroplasties, the prosthesis can be attached to the medullary canal of long bones using methyl methacrylate cement or through bone ingrowth. Cemented fixation of the prosthesis can be complicated by bone-cement implantation syndrome (BCIS) that manifests by marked intraoperative hypotension, bronchoconstriction, hypoxia, cardiac arrhythmias, increased pulmonary vascular resistance, right ventricle failure, or even cardiac arrest. Several mechanisms of BCIS have been proposed, including embolization of bone marrow debris to the pulmonary circulation during pressurization of the medullary canal, toxic effects of circulating methyl methacrylate monomer, and release of cytokines and cyclooxygenase products during reaming of the medullary canal, which can induce pulmonary vasoconstriction and formation of microthrombi. Embolization is believed to occur as a result of high intramedullary pressures during cementing. In cemented arthroplasties, intramedullary pressure can peak at 680 mm Hg, compared to less than 100 mm Hg in arthroplasties without the use of cement. The presence of bone marrow debris has, indeed, been documented in the right heart with intraoperative transesophageal echocardiography (TEE) ( Figs. 64.8 and 64.9 ).
